The disclosure relates to optical coupling, such as among an array of fibers and an array of waveguides within a waveguide circuit, e.g., a planar lightwave circuit (PLC) and/or photonic integrated circuit (PIC) (e.g., silicon photonic circuit). In particular, this disclosure relates to a fiber optic-to-waveguide coupling assembly including an interposer evanescently coupled to a waveguide circuit and edge coupled to optical fibers of a fiber array unit (FAU).
FIG. 1A is a perspective view of a fiber-to-waveguide coupling system 100 (e.g., planar lightwave circuit (PLC) assembly) including a fiber array unit coupler 102 (e.g., FAU coupler) of a fiber array unit 104 and a waveguide coupler 106 of a waveguide assembly 108. The fiber array unit coupler 102 includes a plurality of optical fibers 110 with end faces 112. The waveguide coupler 106 includes a plurality of waveguides 114 with end faces 116. When the fiber array unit coupler 102 is engaged with the waveguide coupler 106, the end faces 112 of the optical fibers 110 are in contact with (or closely proximate to) and aligned with the end faces 116 of the waveguides 114. In this way, the optical fibers 110 and the waveguides 114 are edge coupled permitting optical communication between the fiber array unit 104 and a waveguide circuit 115 of the waveguide assembly 108.
Edge coupling between the optical fibers 110 and the waveguides 114 may require an optical quality edge on the waveguide circuit 115, which adds manufacturing cost and process complexity. Such a configuration may also require precise alignment between the optical fibers 110 and the waveguides 114, which may be difficult, time consuming and/or expensive. Achieving precise alignment may require complex manufacturing processes and/or components which are not compatible with standard electronic integrated circuit assembly processes, such as high throughput pick and place machines used to place surface mount devices onto a printed circuit board (PCB).
FIG. 1B is a cross-sectional view of another fiber-to-waveguide coupling system 100′ for edge coupling. The fiber-to-waveguide coupling system 100′ includes a planar waveguide array 108′ of an interposer 106′ that is intermediate and positioned between a waveguide circuit 115′ and a plurality of optical fibers 110′ of a fiber array unit (FAU) coupler 102′. The interposer 106′ is positioned to edge couple light to or from optical fibers 110′ of the FAU coupler 102′. The fiber-to-waveguide coupling system 100′ avoids the need for an optical quality edge for the waveguide circuit 115′ and allows for surface mounting of the interposer 106′, but still requires actively aligning the FAU coupler 102′ to waveguides 118′ of the interposer 106′ using all six translational and rotational degrees of freedom. Attempts to simplify this complex alignment process and reduce the number of degrees of freedom for highly precise passive alignment may require complicated manufacturing steps. For example, the use of complementary insertion pins and receptacles in a male-female relationship may align the FAU coupler 102′ and the waveguide coupler 106′, but manufacturing of couplers with such insertion pins requires specific relative sizing and placement (using all six translational and rotational degrees of freedom). This may be further complicated when formation of corresponding alignment features requires precise manufacturing of very different materials and different manufacturing processes between respective couplers.
While passive alignment freedom leads to faster, lower cost integrated photonic packages, what is needed is a simple fabrication and assembly compatible with existing processes.
No admission is made that any reference cited herein constitutes prior art. Applicant expressly reserves the right to challenge the accuracy and pertinency of any cited documents.